Dengue-resistance Spreads in Mosquitoes

Researchers engineer a bacterium that can arm the majority of the insect population with dengue resistance, and stop the virus’s spread to humans.

By Edyta Zielinska | January 11, 2012

Larva of Aedes aegyptiWIKIMEDIA COMMONS, ECONT

Australian researchers have added an additional tweak to the strain of bacteria they used to infect mosquitoes carrying the dengue virus, and shown that it can spread effectively throughout a local population of mosquitoes in the wild, according to Nature.

The lab’s earlier work had demonstrated that a strain of Wolbachia pipientis, a bacterium that infects insects, could halt the reproduction cycle of the dengue virus. While the exact mechanism is unknown, the bacteria likely "compete for limited sub-cellular resources required by the virus for replication," lead author Scott O'Neill from Monash University in Melbourne, Australia told Nature.

But the first strain O’Neill’s group used killed not only the virus, but also about half of the mosquito hosts before they could reproduce and pass the disease-stopping bacteria on to their progeny. Slight alterations to the Wolbachia allowed it to remain in the mosquito for roughly the normal lifespan of the insect. Sure enough, when the researchers released the engineered mosquitoes into two Queensland towns last January, the bacteria spread to more than 90 percent of the native population, which has now increased to close to 100 percent. The next step will be to try the mosquitoes in areas where dengue fever is more common, such as Vietnam and Indonesia. Some scientists worry that releasing an engineered mosquito into the wild could have unintended outcomes either on the local ecology, or if the Queensland project fails, on other projects that are attempting to stop the spread of disease at the level of the mosquito or insect vector. (Read more about engineering mosquitoes to control the spread of disease in our October, 2009 feature, Evolution, Revisited.)